Firefly III MCP Server

Update Firefly III Tag

firefly_update_tag

Idempotent

Update an existing tag's description in Firefly III to keep your financial categorization accurate and organized.

Instructions

Update an existing tag's description.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "tag": "<tag>"
    },
    "name": "firefly_update_tag"
  }
}

Input Schema

Name	Required	Description	Default
`tag`	Yes	Current tag name (used as identifier)
`description`	No	Updated description

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.1Apr 7, 2026

TDQS

A3.5/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations indicate the operation is non-destructive and idempotent. The description adds that only the description field is updated (not the tag name itself) and that the tag must be 'existing'. However, it fails to explain idempotency implications, openWorldHint behavior, or what happens if the specified tag does not exist.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is five words, front-loaded with the action verb, and contains no redundancy. Every word serves a distinct purpose: operation (Update), target state (existing), resource (tag), and specific field (description).

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple two-parameter update operation with comprehensive annotations and full schema coverage, the description is minimally sufficient. However, given the lack of output schema, it could benefit from mentioning whether the operation returns the updated tag or simple success status, and behavior when the tag is not found.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 100% schema description coverage, the schema already fully documents both parameters ('tag' as identifier, 'description' as the updated value). The description aligns with but does not substantially augment the schema's semantic information, warranting the baseline score for high-coverage schemas.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb (Update), resource (tag), and specific scope (description). It distinguishes from 'create' by specifying 'existing' tag. However, it does not explicitly differentiate from other update operations in the Firefly family (e.g., update_account), though the tool name handles this.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The phrase 'existing tag' implies a prerequisite (the tag must already exist), suggesting users should use firefly_create_tag for new tags. However, it lacks explicit when-to-use guidance, error handling for missing tags, or mention of the required 'tag' parameter acting as an identifier.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.